public class MyLinkedList {
    public class ListNode{
        int val;
        ListNode prev;
        ListNode next;

        public ListNode(int val) {
            this.val = val;
        }
    }
    public ListNode head;
    public ListNode last;
    //头插法
    public void addFirst(int data){
        ListNode node = new ListNode(data);
        if(head == null){
            head = node;
            last = node;
        }else{
        node.next = head;
        head.prev = node;
        head = node;
        }
    }
    //尾插法
    public void addLast(int data){
        ListNode node = new ListNode(data);
        if ( head == null){
            addFirst(data);
        }else {
            last.next = node;
            node.prev = last;
            last = node;
        }

    }
    //任意位置插入,第一个数据节点为0号下标
    public void addIndex(int index,int data){
        if(index < 0 || index >size()){
            throw new SubScriptError("下标值不合法");
        }
        if(index == 0){
            addFirst(data);
            return;
        }
        if(index == size()){
            addLast(data);
            return;
        }
        ListNode cur = findindex(index);
        ListNode node = new ListNode(data);
        node.next = cur;
        node.prev = cur.prev;
        cur.prev.next = node;
        cur.prev = node;
    }
    private ListNode findindex(int index){
        ListNode cur = head;
        while (index!=0){
            cur = cur.next;
            index--;
        }
        return cur;
    }
    //查找是否包含关键字key是否在单链表当中
    public boolean contains(int key){
        ListNode cur = head;
        while (cur!=null){
            if(cur.val == key){
                return true;
            }
            cur = cur.next;
        }
        return false;
    }
    //删除第一次出现关键字为key的节点
    public void remove(int key){
        if(head.val == key){
            head =head.next;
            if (head!=null) {
                head.prev = null;
            }
            return;
        }
        if(last.val == key){
            last = last.prev;
            last.next = null;
            return;
        }
        ListNode cur = head;
        while (cur != null){
            if(cur.val == key){
                cur.next.prev = cur.prev;
                cur.prev.next = cur.next;
                return;
            }else {
                cur = cur.next;
            }
        }
    }
    //删除所有值为key的节点
    public void removeAllKey(int key){
        if(head.val == key){
            head =head.next;
            if (head!=null) {
                head.prev = null;
            }
        }
        if(last.val == key){
            last = last.prev;
            last.next = null;
        }
        ListNode cur = head;
        while (cur != null){
            if(cur.val == key){
                cur.next.prev = cur.prev;
                cur.prev.next = cur.next;
            }
                cur = cur.next;
        }
        return;
    }
    //得到单链表的长度
    public int size(){
        int count = 0;
        ListNode cur = head;
        while (cur!=null){
            cur = cur.next;
            count++;
        }
        return count;
    }
    public void display(){
        ListNode cur = head;
        while (cur!=null){
            System.out.print(cur.val+" ");
            cur =cur.next;
        }
        System.out.println();
    }
    public void clear(){
        ListNode cur = head;
        while (cur !=null){
            ListNode curnext =cur.next;
            cur.prev = null;
            cur.next = null;
            cur = curnext;
        }
        head = null;
        last = null;
    }
}
